Automatic reclosing circuit breaker system



June 2, 1936. A. H. CURTIS 2,042,925

AUTOMATIC RECLOSING CIRCUIT BREAKER SYSTEM Filed March 5, 1926 Fig].

l I 2 36' I fi 26 25 9? 39 28 25 40 1:328 38 -26 o 4! I 42 .21 2d 32 2 INVENTOR WMMMGM 43 43 31 BM ATTORNEY Patented June 2, 1936 AUTOMATIC RECLOSING cmoorr BREAKER SYSTEM Arthur Herbert Curtis, Bedford, England, assignor, by mesne assignments, to Cutler-Hammer, Inc., Milwaukee, Wis., a

Delaware corporation of Application March 5, 1926, Serial No. 92,426 In Great Britain March 12, 1925 4 Claims. (Cl. 175-294) This invention relates to, and has for its object the provision of improvements in, automatic circuit breakers of the type adapted to open upon the occurrence of overload, to reclose automatically after a given'interval, but to be maintained open indefinitely should the overload or fault persist. The invention consists broadly in the arrangement according to which the means for maintaining the breaker open indefinitely become effective in response to the operation of a device which in turn operates in response to the cumulative eifect of an electric current supplied thereto and is adapted to be supplied with said current for a period depending upon the period of overload.

This device preferably comprises a bimetallic thermal element adapted to be heated by said electric current and the period during which said current is adapted to be supplied to said device is preferably the period during which the circuit breaker is open.

An embodiment of the invention is illustrated in the accompanying drawing and the same will now be described, it being understood that the particular construction and arrangement illustrated are susceptible of various modifications without departing from the scope of the invention as defined in the appended claims.

In this drawingz- Figure 1 is a diagrammatic view of a circuit breaker system in accordance with the invention.

Figure 2 is a side elevation, partly in section and partly broken away, of the circuit breaker proper and the elements immediately associated therewith.

Figure 3 is a front elevation of the same.

Referring to Figure 1 the system therein illustrated comprises a three phase alternating current generator I adapted to feed a load represented by Ll, L2 and L3. Interposed between said generator and said load is a main circuit breaker 2 having upper main contacts 2a and lower main contacts 2b. In rigid relationship with said main contacts 2a and 2b are auxiliary contacts 20, said auxiliary contacts being-adapted to open when said main contacts close and close when said main contacts open. Further auxiliary contacts 2d are also provided in connection with said main circuit breaker, said contacts 2d being interlocked, as will be clear from the drawing so as to positively open when said main contacts close and to be permitted to close under the influence of gravity when said main contacts open. This gravity closure is delayed by means of a one way dash pot 3. Said main circuit breaker 2 is provided with a closing winding 2e adapted upon energization to effect closure of the main contacts.

A controlling relay 4 is provided, said relay having a closing winding 40. and upper and lower contacts 41) and to both of which are adapted to close when said closing winding is energized and open when said closing winding is de-energized. A resistance 5 is permanently connected in series with said closing winding M.

An overload relay 6 is provided, said overload 5 relay comprising normally closed contacts So, an overload coil 6b and an armature 6c. Energization of the overload coil effects lifting of the armature which in turn effects opening of the contacts 6a. The armature however is normally separated from the contacts 611 so that it has to be lifted through a given space before opening said contacts. The armature moreover is delayed in its upward movement by means of a one way dash pot I and therefore the overload coil must be energized a predetermined time before the overload contacts are opened.

Athermo-respbnsive switch 8 is provided, said switch comprising a switch element 8a, a bimetallic thermal element 8b and a heating resistor 80. The switch element to is biased (by gravity or otherwise) to open position and is normally held closed by the engagement of the bimetallic element 8b with an insulating end of a lever extending from said switch element as shown. When 25 the element 8b is heated to a predetermined temperature it disengages said lever, and said switch element 8a is permitted to spring to the open position. A push button 8d is provided for resetting said switch element. A regulating rheostat 9 is 30 permanently connected in series with the heating resistor 80.

The parts above described are connected in circuit as shown in the figure and the operation of the system will now be described. 35

Suppose the generator is operative and is feeding the load, the parts therefore being all in the position shown in Figure 1. The main circuit breaker 2 is closed and three phase connections extend from the generator I to the load Ll, L2 and L3 said connection being traceable via the thick lines of the drawing(a) from the generator through conductor l0 and through the upper contacts 2a of said main circuit breaker to LI (b) from the generator, through overload coil 6b, through conductor II, and through the lower contacts 2b of said main circuit breaker to L2 and (c) from the generator and through conductor l2 to L3.

Prior to closure of main circuit breaker 2 a closing circuit for the controlling relay 4 extends from mainline conductor l0, through conductors I3 and 2|, through the lower contacts 2d of said circuit breaker 2, through conductor 22, through the energizing winding 4a of said controlling relay 4, through resistance 5, through overload contacts to, through conductor I9, through the thermally controlled switch element 8a and through conductors 20 and H to main line conductor I I. Upon closure of relay 4 the contactors 40 thereof provide a maintaining circuit therefor shunting the contactors 2d of main contactor 2,

winding 2e 01' said circuit breaker 2, and through of said controlling relay will open. Opening of upper contacts 4b disestab accordingly opens both its main contacts 2a and 2b thus disconnecting the generator from the load.

The closing circuit for the controlling relay 4 cannot be immediately reestablished upon the breaker 2) after a definite time interval from the circuit of said controlling relay 4. Connections will therefore all be re-established as in Figure 1.

Should the overload have ceased the generator will therefore continue feeding the load as before. Should the overload be still in existence the overwfll once more, subject to the Ga reclosing in consequence short time delay determined by the dash pot 1, open the overload contacts 6a and the above deoperations will be repeated as subject to a manual resetting operation.

Thus, closure of contacts said main contacts 2a and 2?) establishes a circuit through conductors 20 and ll-to the main line conductor H.

As long as the above described opening and closing of the circuit breaker 2 continues, by virtue of the continuation of the overload, this heat- 25 ing resistor 80 will be intermittently energized. The arrangement is such that such intermittent energization has a cumulative effect on the temperature of the bimetallic element 8b. After de-energization of the controlling relay 4 re-energized. Therefore the main circuit breakonly be reclosed by operation of the manual push button 8d. 40

Referring now to Figures 2 and 3 the closing coil 2e of the circuit breaker is adapted to actuate the main contacts 211 and 2b and the auxiliary contacts 20 and 2d through the medium of an armature 25 which armature is mounted so as to 45 pivot about an axis 26. The contacts 2a and 2b consist, as will be clear 6O Midway between its extremities the contact bar 2c carries an insulating sleeve 3| and this sleeve bears against one end of an L lever 32 having a fixed pivotal axis. The other end of this lever engages underneath a projection 33 65 projecting from the aforesaid rod 30 and thereby holds the dash pot element 29 and the contact bar 2d at their uppermost limits.

The position of Figures 2 and 3 corresponds to the position of Figure 1. That is to say the closing coil 2c is energized, the armature is at its attracted position, the contacts 2a and 2b are closed and the contacts 2c and 2d are open.

When the closing coil 2e is de-energized the armature 25 is adapted to rotate about its axis in a counter clockwise direction (according to Figure 2) to its unattracted position. Accordingly the brush and plate of the contacts 2a and 2b disengage, the contact bar 2c engages the yielding contacts 20 and the L lever 32 rotates in a clockwise direction thereby disengaging the projection 33 and permitting the dash pot element 29- and contact bar 2d to fall slowly until said contact bar 2d engages its contacts 2d after a predetermined interval. Thus the functions previously described with reference to Figure 1 are effected.

It should be mentioned that the L lever 32 is spring biased in a clockwise direction, it being thereby ensured that the said lever and also the armature 25 will, upon de-energization of the coil 20 rotate as stated.

Associated with each of the pairs' of contacts 2a and 2b is a pair of sparking contacts-viz. a movable contact 34 and a fixed contact 35-which are adapted to make contact a little before and break contact a little after the respective pair of contacts 2a or 2b. Flanking each of these pairs of sparking contacts-one at each side thereof as shown are two blowout cheeks 35 of fireproof insulating material. Blowout coils 31 are also provided in series respectively with the fixed sparking contacts 35. These blowout cheeks and blowout coils are substantially in accordance with known practice and further description thereof has not been deemed necessary.

Describing now certain further constructional details illustrated in Figures 2 and 3, the securement of the arm 28 to the armature 25 is effected by co-engagement of bolts 38 integral with said arm within bossed holes in the ends of lugs 39 integral with said armature 25. Insulating packing 40 is interposed between said bolts and said bossed holes so that said arm 28 is insulated from said armature 25. The movable sparking contacts 34 are yieldably mounted to the respective arms 28 in a well known manner which will be readily recognized from the drawing. The fixed sparking contacts 35 are mounted to the base or panel and are formed with the respective blowout coil integral therewith and in series between said contacts and their points of mounting to the panel.

The bridging contact bar 20 bears as shown in insulating collars 4| carried by lugs 42 integral with the armature 25. The bridging contact bar 2d is suitably insulated from the rod 30.

The outlet 43 from the cylinder of the dash pot 1 3 is made adjustable so that the timing of said dash pot may be adjusted.

Other constructional details are deemed clear from the drawing.

What I claim and desire to secure by Letters Patent is:

1. In a circuit, a main said circuit, means for automatically reclosing the said breaker, means for rendering said reclosing means inoperative comprising a switch,

breaker located in the a resistance element and a thermostat element,

the thermostat element located in operative relation to the resistance element, the resistance element energized when the main breaker is open to heat the thermostat element to cause the thermostat element, after a certain time, to operate the switch to render the said reclosing means permanently inoperative if the main breaker remains open for a too long time interval or an aggregate of successive open periods substantially equal to the said time interval.

2. An automatic reclosing circuit breaker system comprising a circuit breaker proper, a controlling relay for controlling the operation of said circuit breaker, said controlling relay having an interlock whereby it maintains itself at the position corresponding to closure of the circuit breaker proper, an overload relay adapted, upon response, to effect operation of said controlling relay to the position corresponding to opening of said circuit breaker proper, an interlock on the circuit breaker proper adapted after a predetermined time interval subsequently to the opening of said circuit breaker to establish connections for return of said controlling relay to the position corresponding to closure of said circuit breaker proper whereby all the above parts return to the first position, and a thermo-responsive switch adapted to be energized only when the circuit breaker proper is open, and upon response to prevent reclosure of said circuit breaker proper substantially as and for the purpose specified.

3. An automatic reclosing circuit breaker system according to claim 2 wherein said overload relay is adapted to respond only upon continuance of the overload for a predetermined time.

4. An automatic reclosing circuit breaker system, comprising main contacts normally biased to open position and auxiliary contacts normally biased to closed position, a winding adapted when energized to efiect closure of said main contacts and opening of said auxiliary contacts, a control relay having contacts normally biased to open position and adapted when closed to complete the energizing circuit of said winding, an operating winding for said relay and means requiring closure of certain of said auxiliary contacts to effect operating energization of said last men tioned winding when said circuit breaker is open, certain of the contacts of said relay being adapted to provide a maintaining circuit for the latter independently of said auxiliary contacts, an overload relay adapted upon response to interrupt the maintaining circuit for said relay winding whereby the relay contacts are opened to interrupt the energizing circuit of said first mentioned winding, said main contacts when opened being adapted to interrupt the energizing circuit of said overload relay and to permit reclosure of certain of said auxiliary contacts, but subject to a delay, to thereby again eifect completion of the energizing circuits of said control relay winding and said first mentioned winding in sequence, a switch biased to open position and adapted when opened to prevent completion of the energizing circuit of said control relay winding pending manual reclosure of the former, a bimetallic thermostatic element to latch said switch in closed position, a heating coil associated with said element, and other of said normal y closed auxiliary contacts being adapted during open positioning 'of said main contacts to complete an energizing circuit for said coil, said thermostatic element being responsive to the intermittent and cumulative heating effect of said coil to effect release of said switch after a given time interval under the conditions aforementioned.

ARTHUR. HERBERT CURTIS. 

